Power door latch assembly

ABSTRACT

A power door latch assembly consists of a ratchet ( 50 ) for engaging a door striker, a pawl ( 52 ), a rotary actuator ( 54 ) for rotating the ratchet ( 50 ) towards the closed position and for disengaging the pawl ( 52 ) and a drive actuator ( 96 ) for driving the rotary actuator ( 54 ). The drive actuator ( 96 ) includes a prime mover ( 98 ) an output member ( 104 ) in engagement with the rotary actuator ( 54 ), and releasable coupling ( 102 ) coupled between the prime mover ( 98 ) and the output member ( 104 ) for selectively transferring torque between the prime mover ( 98 ) and the rotary actuator ( 54 ). A drive controller ( 108 ) is coupled to the releasable coupling ( 102 ) and is configured for disengaging the prime mover ( 98 ) from the rotary actuator ( 54 ) when the ratchet ( 50 ) is disposed in either the open or closed positions.

This application is a 371 of PCT/CA00/00164 filed Feb. 18, 2000, whichclaims benefit to provisional application 60/120,585 filed Feb. 18,1999.

FIELD OF THE INVENTION

This present invention relates to a latch assembly for and unlatching amember to and from a pillar in particular, the present invention relatesto a powder door latch assembly for securing and unsecuring a vehicledoor.

BACKGROUND OF THE INVENTION

A typical motor vehicle door is mounted in a door frame on the vehicleand is movable between open and closed positions. Usually the door isheld in a closed position by the latching engagement between aspring-biased ratchet pivotally mounted inside the door latch and aU-shaped striker secured to the door frame. The ratchet is most oftenspring-biased toward the unlatched position to release the striker andis maintained in the latched position to hold the striker by aspring-biased pawl or other mechanical structure. The ratchet cannotpivot to release the striker until the pawl is moved.

The majority of these door latches are exclusively manually operatedboth to unlatch the door and to relatch the door. Typically, the manualrelease handles are provided on the inside and outside of the door torelease the ratchet from the striker by moving the pawl so that the doorcan be opened. The door is closed and relatched by manually pivoting thedoor so that the ratchet impacts the striker with sufficient force topivot the ratchet to the latched position against the spring forceexerted by the ratchet spring.

It is often difficult, however, to completely close and latch manuallylatching vehicle doors on current model vehicles because the desire toreduce vehicle weight and to improve fuel economy has led engineers todesign vehicles with relatively thin and lightweight doors. Oftenrelatively hard door seals are used with these thin, lightweight doorsto improve sealing around the door, particulary at high driving speeds.Because many vehicle doors are relatively lightweight and haverelatively hard door seals, many vehicles doors often have insufficientinternal energy when pushed closed to compress these hard door seals andfully pivot the ratchet to the latched position to latch the door.

Power assisted door latch assemblies have been developed to overcome theproblems associated with latching doors with lightweight constructionand hard door seals. Power assisted door latch assemblies allow lowinternal energy or soft closure of the lightweight doors without theneed to slam the door even with the increased seal pressure that resultsfrom relatively hard door seals. Existing power associated door latchassemblies typically function to latch a vehicle door in one of twoways: 1) by forcing the ratchet to pivot in the closing direction afterengagement with the striker or 2) by forcing the striker to move in adoor-closing direction after the striker is fully engaged with theratchet.

Use of either type of power associated door latch assembly decreases thenoise associated with door closing and decreases the manual effortneeded to completely close the door. Power assisted door latchassemblies are disclosed by Ishikawa (U.S. Pat. No. 4,986,579), Kobayahi(U.S. Pat. No. 5,273,324) and Dowling (U.S. Pat. No. 5,520,425). InIshikawa, the door latch assembly includes an electric motor forrotating the spring-biased ratchet from the partially closed to thefully closed position, and an electric switch for activating anddeactivating the electric motor. In Kobayashi, the door latch assemblyincludes a rotatable lever for rotating the ratchet plate into the fullyclosed position, an electric motor manipulating the lever, and amechanical linkage extending between the lever and the ratchet plate forrotating the ratchet plate into the fully closed position. In Dowling,the door latch assembly includes a motor driven gear, and a flexiblewire extending between the driven gear and the ratchet for rotating theratchet from the partially closed to the fully closed position. However,Ishikawa requires a complex rotary actuator for operating the switch,whereas the mechanical link and the flexible wire used respectively inKobayshia and Dowling inefficiently transfers mechanical torque betweenthe electric motor and the ratchet plate.

Latch assemblies which provide both power assisted opening and powerassisted closing are also in use. In these power assisted latchassemblies, the same source of power, typically an electric motormounted within the vehicle door, is used both to open the latch and toclose the latch. The mechanical locking mechanism and some door openinghandles can be eliminated from the vehicle door when these latchassemblies are used.

Power assisted opening and closing latch assemblies are taught byBernard (U.S. Pat. No. 4,664,430), Kleefeldt (U.S. Pat. No. 4,518,180)and Tamiya (U.S. Pat. No. 5,232,253). These types of latching assemblyare often advantageously used with powered sliding vehicle doors inwhich the latch must be released before the power door opening mechanismcan be actuated to open the door. Bernard uses a cylindrical ratchetplate and a disc rotatably mounted on a common shaft, a pawl pivotallymounted on the disc for engagement with the ratchet plate, and anelectric screw drive for rotating the disc between an open latchposition and a close latch position. Kleefeldt uses a motor-driven gearand a sliding toggle linkage mechanically coupled to the driven gear foropening and closing the ratchet Tamiya uses a rack-driven link forrotating the ratchet from the open position to the closed position, anda lever coupled to the link for releasing the pawl from the ratchet toallow the ratchet to be rotatably driven back to the open position.However, Bernard stresses the electric motor by using the motor as braketo retain the ratchet plate in the closed position, whereas the latchingmechanisms taught by Kleefeldt and Tamiya may not be reliable inenvironments where the door is forcefully closed into the latch. Also,the sliding toggle linkage used by Kleefeldt limits the mechanicaltorque which is ultimately applied to the ratchet

Accordingly, there remains a need for a simple, cost-effectivepower-assisted door latch assembly which efficiently transfers torquefrom the electric motor to the ratchet Further, there remains a need fora power-assisted door latch assembly which limits the stress applied tothe electric motor by the ratchet.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a power door latchassembly which addresses some of the deficiencies of the prior art

The power door latch assembly, according to the present invention,comprises a ratchet for engaging a door striker, a pawl for engaging adetent surface provided on the ratchet for selectively resistingrotation of the ratchet towards the open position, a rotary actuator forrotating the ratchet towards the closed position and for disengaging thepawl from the detent surface, and a drive actuator for driving therotary actuator. The drive actuator includes a prime mover, an outputmember in engagement with the rotary actuator, and a releasable couplingcoupled between the prime mover and the output member for selectivelytransferring torque between the prime mover and the rotary actuator. Thepower door latch assembly also includes a drive controller forcontrolling operation of the drive actuator. The drive controller iscoupled to the releasable coupling and is configured for disengaging theprime mover from the rotary actuator when the ratchet is disposed ineither the open or closed positions.

According to the preferred embodiment of the invention, the door latchassembly provides for the power assisted opening and closing of avehicle door with respect to a vehicle door frame between a closedposition wherein the door is latched to a striker mounted on the doorframe and an opened position in which the door is unlatched from thestriker. The door latch assembly has a ratchet which cooperates with amouth of a housing to releasably retain the striker. The door latchassembly also includes a pivotal pawl mounted in cooperating relationwith the ratchet for biased movement into a holding position wherein theratchet is held (1) in the secondary latched position against movementtoward the unlatched position and (2) in the primary latched positionagainst movement toward the secondary latched position. The pawl can bemoved out of the holding position into a releasing position to allow theratchet to move toward and into the unlatched position. The door latchassembly further includes a sector gear constructed and arranged to bemoved from a null position in one direction through a closing strokeinto a closing position and from the closing position through a returnstroke to the null position and from the null position in an oppositedirection through an opening stroke into an opening position and fromthe opening position through a return stroke into the null position. Anactuator assembly includes a reversible electric motor and a clutchassembly for selectively driving the sector gear. The electric motor isoperable (1) when energized to rotate in one direction to drive thesector gear through the closing stroke thereof and (2) when energized torotate in an opposite direction to drive the sector gear through theopening stroke thereof. The sector gear has a closing arm constructedand arranged to cause a movement of the ratchet from the secondarylatched position thereof to the primary latched position thereof. Thesector gear has an opening arm constructed and arranged to cause amovement of the pawl from the holding position thereof to the releasingposition thereof to release the ratchet.

Preferably, the sector gear has a spring for urging the sector gear tomove through the return strokes thereof from opening and closingpositions thereof when the actuator is de-energized.

Preferably the door latch assembly includes an energizing closing switchconstructed and arranged to be actuated in response to the movement ofthe ratchet into the secondary latched position thereof to energize theelectric motor to thereby move the sector gear through a closing strokeso that the closing arm causes the ratchet to move from the secondarylatched position thereof into the primary latched position thereof and aclosing de-energizing switch constructed and arranged to be actuated inresponse to the movement of the ratchet into the primary latchedposition thereof to de-energize the electric motor and allow the springsystem to effect a return stroke of the sector gear. The power operateddriving assembly further includes a manually operable opening energizingswitch constructed and arranged to energize the electric motor inresponse to a manual actuation thereof to move the sector gear throughan opening stroke so that the opening structure thereof causes theratchet to move out of the primary position thereof to allow the door tobe moved into an open position and a timer closing de-energizing switchconstructed and arranged to be actuated in response to the movement ofthe pawl into the releasing position thereof to de-energize the electricmotor after a predetermined time and allow the spring system to effect areturn stroke of the sector gear.

Preferably, the ratchet and the sector gear am pivotally mounted about acommon axis and the pawl is pivotally mounted about an axis that isparallel to the common axis.

Preferably, the door latch assembly includes a housing having a strikerreceiving opening therein constructed and arranged to be mounted in thevehicle door so that the opening receives the striker during a doorclosing movement. The ratchet is pivotally mounted on the housing withthe striker engaging structure facing outwardly within the opening whenthe ratchet is in the unlatched position. The latching structure extendswithin the opening when the ratchet is in the latched positions. Thehousing carries the pawl, the sector gear and the power operated drivingassembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only,with reference to the accompanying drawings, in which:

FIG. 1 is an elevational view of the left side of a conventionalfour-door vehicle;

FIG. 2 is an isolated fragmentary perspective view of the interior of afront door of the vehicle shown in FIG. 1;

FIG. 3 is a perspective view at a first side of a power assisted doorlatch assembly embodying the principles of the present invention;

FIG. 4 is a perspective view of a second side of the power assisted doorlatch assembly shown in FIG. 3;

FIG. 5 is a perspective view similar to FIG. 3 of the door latchassembly with a first cover and a second cover removed;

FIG. 6 is a perspective view similar to FIG. 4 of the door latchassembly with the second over removed;

FIG. 7 is a schematic view showing a power operated driving assembly, apower source, a voltage source and controller for the door latchassembly;

FIG. 8 is an elevational view showing a plurality of parts of the doorlatch assembly including a ratchet, a pawl, a sector gear, a firstswitch member and a second switch member in a primary latchedconfiguration with a conventional striker shown in sectional viewmounted on a door frame shown in fragmentary view,

FIG. 9 is a view similar to FIG. 8 showing the pawl in a releasingposition and the sector gear in an opening position;

FIG. 10 is a view similar to FIG. 8 showing the door latch assembly inan unlatched position;

FIG. 11 is a view similar to FIG. 8 showing the door latch assembly in asecondary latched position;

FIG. 12 is a view similar to FIG. 11 showing the door latch assembly ina secondary latched position and showing the sector gear partiallyrotated in a closing direction; and

FIG. 13 is a view similar to FIG. 12 showing the ratchet in a primarylatched position and showing the sector gear fully rotated in a closingdirection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a left side elevational view of the exterior of aconventional motor vehicle that has a front door 12 and a back door 14.Each door 12, 14 has an exterior handle 16 and a door latch openingbutton 18. The front door 12 has a conventional key-operated lockcylinder to lock and unlock the door 12.

A power operated door latch assembly 22 constructed according to theprinciples of the present invention is mounted on each door of thevehicle 10 for the power assisted latching and unlatching of each door.

FIG. 2 shows an isolated view of the inside of the front door 12. Twohinges 24 are secured to a first inner edge 28 of the door 12 topivotally mount the door 12 to a door frame on the vehicle 10 in aconventional manner so the door can be moved between open and closedpositions. A power operated door latch assembly 22 is mounted on asecond outer edge 30 of the door. The door 12 has an interior doorrelease switch 32 to unlatch the door latch assembly 22 with powerassistance and an interior manual door release handle 34 to manuallyunlatch the door 12 using a manual override.

A conventional U-shaped striker is rigidly secured to the door frame ofthe vehicle 10 in a conventional manner. When the door 12 is moved tothe closed position, the door 12 pivots into the door frame and the doorlatch assembly 22 impacts the striker to latch the door 12.

Referring to FIGS. 3 and 4, the door latch assembly 22 includes ahousing 36 and a first cover 38 and second cover 40 secured to the firstcover 38. The covers 38, 40 are secured to the housing 36 byconventional staking pins 42, 44 or other suitable fasteners. Thehousing 36 engages threaded holes 46 to mount the door latch assembly 22to a door 12 with conventional bolts or other suitable means. Housing 36has a mouth structure 31. Tab 93 on the second cover 40 extends througha slot 95 in the first cover 38 and two tabs 97, 99 on the first cover38 clip over the edge of the second cover 40 at 101, 103 to close thedoor latch assembly 22.

Referring to FIG. 5, the housing 36 has a conventional bushing 58 forrotatably mounting the ratchet 50 on pin 44 (FIG. 6) between anunlatched or open position and a primary latched or closed position.Ratchet 50 has a conventional detent fork structure having a notch 110presenting a primary detent surface 126. The ratchet 50 has a secondarydetent 128 spaced circumferentially from the primary detent 126. Theratchet 50 has a contoured edge diametrically opposite the notch 110presenting a cinch drive area 132 and a release clearance area 114.Ratchet 50 cooperates with the mouth 31 to engage and cinch the striker106 (FIG. 8) to hold the door closed.

Housing 36 has a conventional bushing 56 for rotatably mounting the pawl52 on pin 42 (FIG. 6). Arcuate slot 66 receives connecting arm 64 andallows travel of the pawl 52 between a latching position and a fullrelease overtravel position. Pawl spring 68 extends between the housing36 and the pawl 52 to bias the pawl 52 against the ratchet 50 to followthe contours of the circumference thereof. Housing 36 has a channel forretaining the pawl spring 68.

Referring to FIG. 6, a sector gear 54 is commonly mounted on pin 44 on aside of the housing opposite the ratchet 50. Sector gear 54 is mountedin such a manner that the sector gear 54 is able to rotate relative toor independently of the ratchet 50. The sector gear 54 has an opening orreleasing arm 70 which extends tangentially from a toothed portion 55.The sector gear 54 also has a closing or cinching arm 72 which extendsaxially from the toothed portion 55. Coil springs 74 are mounted aroundsector bearing cylinder 59 with a first end 77 engaging the housing 36and a second end 79 engaging the sector gear 54. Springs 74 bias sectorgear 54 into a null position.

Housing 36 has an arcuate slot 57 through which closing arm 72 extendsfor engagement with cinch drive area 132 of ratchet 50. As sector gear54 rotates, it will rotate independently of the ratchet 50 until itengages the cinch drive area 132. In the release direction, the travelof sector gear 54 is not obstructed by the ratchet 50 due to the releaseclearance area 114. Thus, sector gear 54 has a “lost motion” relative tothe ratchet 50.

A release lever 62 is commonly mounted on housing bushing 56 on oppositesides of the housing 36 from the pawl. Housing 36 has an arcuate slot 66through which connecting arm 64 (FIG. 5) extends coupling the pawl 52and the release lever 62 together for pivotal movement as a single unit.Release lever 62 has a hub from which arms 112, 117 (FIG. 8), 134, 136and 137 radially extend.

Pin 42 provides pivotal support for the pawl 52 and release lever 62 andthe pin 44 provides pivotal support for the ratchet 50 and the sectorgear 54. Therefore, the pin 44 defines a rit pivot axis for both theratchet 50 and the sector gear 54 and the pin 42 defines a second pivotaxis for the pawl 52 and release lever 62. These two axes areessentially parallel.

A first electrical switch 76 (FIG. 5) is mounted on the housing 36 andpositioned to engage the outer cam surface of the release clearance area114 as the ratchet 50 rotates. The pivotal movement of ite ratchet 50will switch or toggle the switch 76 between an “on” state and an “off”slate. A second electrical switch 78 is mounted on housing 36 andpositioned to engage arm 112 of the release lever 62. The pivotalmovement of the release lever 62 will switch or toggle the switch 78between an “on” state and an “off” state. Each switch 76, 78 has twoconventional electrical connectors 81 (FIG. 3) to connect the switchesto a controller 108 (FIG.

Wire 80 and bowden wire 82 engage arm 137 of release lever 62. The outersheath of the bowden wire 82 is mounted to the housing to effectactuation of the bowden wires. Each end of the wires 80, 82 has a cap87, 89 which allows the wires 80, 82 to slide relative to the releaselever 62. Thus, wires 80 and 82 do not interfere with the movement ofthe pawl 52 between the holding and releasing positions during powerassisted door opening and closing.

Referring to FIG. 7, actuator 96 is mounted on the face of the plate 40.Actuator 96 includes a motor 98 and a clutch assembly to selectivelydrive the sector gear 54. The second cover 40 has an opening 48 (FIG. 4)through which a drive shaft 100 extends A drive gear 104 is mounted onthe drive shaft 100 and engages the sector gear 54 to provide torqueamplification for movement of the sector gear 54 and the pawl 52. Themotor 98 and clutch assembly 102 are energized by the vehicle'selectrical system which is schematically represented as a voltage source107. The motor 98, clutch assembly 102 and the drive shaft 100 aremounted within the door 12. A portion of the drive shaft 100 is carriedin the door latch assembly 22 to support the drive gear 104 in thehousing 36 and engage the sector gear 54 with the drive gear 104.

A controller 108 controls the motor 98 and clutch assembly 102 byenergizing and de-energizing the same in response to switching signalsfrom the switches 18 and 32 on the door 12, a remote control 199 and theswitch members 76, 78 in the door latch assembly 22.

The covers 38, 40 are preferably made of steel or other appropriatematerial. The ratchet 50 and first pawl member 52 are preferably made ofsteel or other suitable metal, having a plastic cover 94. The releaselever 62 and the sector gear 54 can be made of any suitable plastic ormetal. The conventional bushings 56, 58 are integral with the housing 36and are preferably a composite material such as nylon.

The Primary Latched Position

FIG. 8 shows the neutral or equilibrium configuration of the door latchassembly 22 when the door is closed and latched. The ratchet 50 is in aprimary latched position and the striker 106 is held in a notch 110 inthe ratchet 50 to hold the door closed. The ratchet 50 is held in theprimary latched position by the pawl 52.

Arm 112 on the release lever 62 holds the switch 78 in a depressedposition. Release clearance area 114 of the ratchet 50 maintains thefirst switch 76 in a depressed position. The sector gear 54 is in thenull position.

There is a small gap or design clearance 116 between the opening arm 70on the sector gear 54 and arm 117 when the latch assembly 22 is in theprimary latched position and the sector gear 54 is in the null position.

In this position, the clutch assembly 102 is de-energized to prevent anytorque from the ratchet 50 or the sector gear 50 from being applied tothe motor 98.

Unlatching and Opening the Door with Power Assistance

To unlatch the door latch assembly 22 with power assistance, any one ofthe switches 18 or 32 on the door 12 or a switch 119 on the remotecontrol 199 is actuated. Each switch 18, 32, 119 functions as anenergizing switch and is independently operable to energize the motor99. When the motor and clutch assembly 102 are energized, the motor 98rotates the drive gear 104 in a first rotational direction to drive thesector gear 54 out of the null position in an opening direction throughan opening stroke to an opening position. The opening direction of thesector fib gear 54 is the counterclockwise direction in FIGS. 8-9.

As the sector gear 54 pivots from the null position to its openingposition, the releasing arm 70 contacts the arm 117 of release lever topivot the pawl 52 from its latching position to its releasing position.Ratchet 50 pivots from the primary latched position to an unlatchedposition to release the striker 106 so the door can be opened.

Although the ratchet spring 118 provides enough force to pivot theratchet 50 from the primary latched position to the unlatched positionwhen the pawl 52 is moved to the releasing position, it can beunderstood that the seal pressure exerted by the door seal on the dooralso tends to move the door latch assembly 22 and the striker apart whenthe door is unlatched which tends to rotate the ratchet 50 to theunlatched position. However, it will also be appreciated that due to thetorque amplification of the drive gear 104 acting upon the sector gear54, the potential energy stored in the ratchet spring 118 will begreater than prior art devices. Consequently, the ratchet 50 will beable to pivot to the unlatched position with greater force than priorart devices and without increasing the size of the motor 98.

When the pawl 52 is in the releasing position, the arm 112 is moved awayfrom the second switch 78 to toggle the second switch 78. When theratchet 50 pivots from the primary latched position to the unlatchedposition, the cam surface of the release clearance area 114 of theratchet 50 moves out of contact with the first switch 76 to toggle thefirst switch 76. In response to the toggling of the first switch 76, thecontrol circuitry 108 de-energizes the motor 98. The actuator 96 holdsthe sector gear 54 in its opening position until the ratchet 50 haspivoted to the unlatched position. When the clutch assembly 102 isdisengaged, the sector gear 54 pivots from the opening position througha return stroke back to its null position under the spring forceprovided by one of the sector springs 74. Consequently, any torque fromthe ratchet 50 or the sector gear 50 is precluded from being applied tothe motor 98.

Closing and Relatching the Door with Power Assistance

Referring to FIGS. 10 to 13, the door latch assembly 22 engages striker106 which enters the mouth 31 and engages the ratchet 50 whichresponsively pivots from the unlatched position toward the primarylatched position. Because of the door seal pressure and the relativelylightweight of the vehicle door, the door may not have sufficientmomentum to rotate the ratchet 50 all the way to the primary latchedposition.

Usually, the ratchet 50 is rotated to allow the pawl 52 to abutsecondary stop 128. The ratchet 50 is retained in the secondary latchedposition. When the door latch assembly 22 is in the secondary latchedposition, the striker 110 is captured in the notch 110 and the door ispartially closed and cannot be reopened without moving the pawl 52 toits releasing position.

When the pawl 52 engages the secondary stop 128, the arm 112 depressesthe second switch 78. In response, the controller 108 energizes themotor 98 and clutch assembly 102. The motor 98 rotates the drive gear104 in a second direction to cause the sector gear 54 to pivot in aclosing direction through a closing stroke in a closing direction. Thecinching arm 72 on the sector gear 54 contacts cinching stop 132 of theratchet 50 so that continued movement of the sector gear 54 in theclosing direction pivots or cinches the ratchet 50 from the secondarylatched position to the primary latched position. The pawl 52 engagesprimary detent 126 to retain the ratchet 50 in the primary latchedposition.

When the ratchet 50 returns to the primary latched position, thereleasing stop 114 of the ratchet 50 depresses and toggles the firstswitch 76. Both switches 76, 78 are now depressed. The first switch 76functions as the closing de-energizing switch which signals thecontroller 1108, in responsive to the movement of the ratchet 50 movinginto the primary latched position, to de-energize the motor 98 anddisengage the clutch assembly 102. When the clutch assembly 102 isde-energized, springs 74 return the sector gear 54 from the closingposition through a return stroke to the null position. The drive gear104 and the drive shaft 100 freely rotate with the sector gear 54 as itreturns to the null position. When the sector gear 54 is back in thenull position, the door latch assembly 22 is again in the neutral orequilibrium position with any torque from the ratchet 50 or the sectorgear 50 being precluded from being applied to the motor 98.

Unlatching and Opening the Door with Manual Override

The opening button 18 functions as an electrical switch when it ispartially depressed through its actuation stroke and functions as amechanical release means when it is fully depressed through itsactuation stoke. Therefore, the opening button 18 is used to open thedoor with power assistance by partially depressing the button 18 throughits actuation stroke and is used to open the door 12 manually with amechanical override by fully depressing the button 18 through its fullactuation stroke. The interior door release handle 34 on the inside ofthe door 12 is used to unlatch the door 12 manually with mechanicaloverride.

The interior door release handle 34 is operatively connected throughBowden wire 80 to the pawl 52. By actuating the interior door releasehandle 34, the Bowden wire 80 is pulled to move the pawl 52 from itsholding position to its releasing position to disengage the pawl 52 fromthe ratchet 50. The ratchet 50 then moves to its unlatched positionunder the spring force of the ratchet spring 118 and the seal load onthe door 12.

The button 18 in the door 12 is mechanically linked in a conventionalmanner to the release wire 82. If the button 18 is fully depressed, itpulls the wire 82 in a direction to move the pawl from its holdingposition to its rotating position to release the ratchet 50.

It can be appreciated that the manual override provided by the button 18and the interior handle 34 can release the ratchet 50 from either theprimary latched position or secondary latched position to open the door12. Each manual release 18, 34 functions independently and each holdsthe pawl 52 in the releasing position as long as the manual release 18or 34 is held in an actuated position by the person opening the door 12.

It is contemplated to use many conventional manual release handles tounlatch the door latch assembly 22. It is also contemplated to use thedoor latch assembly 22 can also be used with any conventional manual orpower operated door locking and unlocking system.

It can be understood that to close the open door and relatch the same inthe primary latched position without power assistance, for example, inthe event of a power failure, the door 12 is simply closed with greaterforce than is ordinarily used when power assistance is available. Themanual closing force is applied to the door 12 must be sufficient torotate the ratchet 50 to the primary latched position so the pawl 52 canmove back into its holding position and engage the first tooth portion109 of the ratchet 50. The door 12 must be closed hard enough tosufficiently compress the door seal on the door frame to allowrelatching.

It is understood that the illustrated operation is exemplary only andnot intended to be limiting.

The latch assembly 22 can be used in other applications. The door lathassembly can be used, for example, on a powered sliding door openingmechanism can start. It is contemplated to use the door latch assemblyin a vehicle door which includes a power mechanism to move the door fromthe open position to the secondary latched position with powerassistance.

The above-described embodiment of the invention is intended to be anexample of the present invention and alterations and modifications maybe effected thereto, by those of skill in the art, without departingfrom the scope of the invention, as defined in the appended claims.

1. A power door latch assembly for engaging a door striker, comprising:a ratchet for engaging the striker, the ratchet being rotatable betweena closed position and an open position and including at least one detentsurface and biasing member for biasing the ratchet towards the openposition; a pawl for engaging the at least one detent surface toselectively resist rotation of the ratchet towards the open position; arotary actuator for rotating the ratchet toward the closed position andfor disengaging the pawl from the at least one detent surface; a driveactuator including a prime mover, an output member in engagement withthe rotary actuator, and a clutch coupled between the prime mover andthe output member for selectively transferring torque between the primemover and the rotary actuator; a drive controller for controlling theoperation of the drive actuator, the drive controller being coupled tothe clutch and being configured for disengaging the prime mover from therotary actuator when the ratchet is disposed in one of the closed andopen positions; said rotary actuator having a cinching arm engaging saidratchet upon rotation of said rotary actuator in a first sense to rotatesaid ratchet towards the closed position, and said rotary actuatorhaving a relating arm engaging said pawl upon rotation of said rotaryactuator in a second sense opposite said first sense to disengage saidpawl from the at least one detent surface; a release lever including anarm extending out therefrom, said release lever pivotally secured tosaid pawl such that said release lever rotates when said pawl rotates; afirst switch for selectively operating said clutch when said ratchet isdisposed in the closed position, said first switch stopping said primemover only when said first switch is closed; and a second switch forstarting operation of said prime mover, said second switch actuated bysaid arm of said release lever only when said pawl engages said detentsurface.
 2. The power door latch assembly according to claim 1, whereinthe rotary actuator is rotatable through a null position wherein therotary actuator is disengaged from the ratchet and the pawl.
 3. Thepower door latch assembly according to claim 2, wherein the drivecontroller is configured for disengaging the prime mover from the rotaryactuator when the rotary actuator is disposed in the null position. 4.The power door latch assembly according to claim 3, wherein the rotaryactuator includes a lost motion linkage for allowing limited rotationalmovement of the ratchet relative to the rotary actuator when the ratchetis disposed in the open position.
 5. The power door latch assemblyaccording to claim 4, wherein one of the at least one detent surfaces isdisposed for providing in cooperation with the pawl a partially openposition between the open and closed positions, and the limitedrotational movement is provided between the open and partially openpositions.
 6. The power door latch assembly according to claim 5,wherein said ratchet includes a cam surface disposed for engagement withthe first switch when the ratchet is disposed in the closed position. 7.The power door latch assembly according to claim 6, including a manualrelease coupled to the pawl for releasing the pawl from the ratchet uponactivation of the manual release.
 8. The power door latch assemblyaccording to claim 7, wherein the ratchet is disposed for rotation abouta first axis, and the pawl is disposed for rotation for about a fixedaxis parallel to the first axis.
 9. The power door latch assemblyaccording to claim 8, wherein the drive actuator is disposed forrotation about the first axis.